We don't need a chatbot from apple.
We need better siri.
Example: I use warp terminal, which has AI built in. It'll do things like give you correct command syntax from english query, like "download audio only best format from youtube". The other day, I was trying to switch audio device through the terminal and failed. It jumped in and said "looks like you're trying to switch audio device and command failed b/c device couldn't be found. Let me run the command to list the devices... I see the problem. There's a trailing space in the device name. You didn't include it, here's the correct command." I would've been banging my head against the wall with that one.
Obviously, something like that would be much harder with a gui. But that's the sort of thing apple could do when they have complete control of the system and access to your data.